package org.bouncycastle.asn1;

import java.io.IOException;
import java.math.BigInteger;

import org.bouncycastle.util.Arrays;

public class DERInteger extends ASN1Object {
    byte[] bytes;

    /**
     * return an integer from the passed in object
     * 
     * @exception IllegalArgumentException
     *                if the object cannot be converted.
     */
    public static DERInteger getInstance(Object obj) {
        if (obj == null || obj instanceof DERInteger) {
            return (DERInteger) obj;
        }

        throw new IllegalArgumentException("illegal object in getInstance: "
                + obj.getClass().getName());
    }

    /**
     * return an Integer from a tagged object.
     * 
     * @param obj
     *            the tagged object holding the object we want
     * @param explicit
     *            true if the object is meant to be explicitly tagged false
     *            otherwise.
     * @exception IllegalArgumentException
     *                if the tagged object cannot be converted.
     */
    public static DERInteger getInstance(ASN1TaggedObject obj, boolean explicit) {
        DERObject o = obj.getObject();

        if (explicit || o instanceof DERInteger) {
            return getInstance(o);
        } else {
            return new ASN1Integer(ASN1OctetString.getInstance(obj.getObject())
                    .getOctets());
        }
    }

    public DERInteger(int value) {
        bytes = BigInteger.valueOf(value).toByteArray();
    }

    public DERInteger(BigInteger value) {
        bytes = value.toByteArray();
    }

    public DERInteger(byte[] bytes) {
        this.bytes = bytes;
    }

    public BigInteger getValue() {
        return new BigInteger(bytes);
    }

    /**
     * in some cases positive values get crammed into a space, that's not quite
     * big enough...
     */
    public BigInteger getPositiveValue() {
        return new BigInteger(1, bytes);
    }

    void encode(DEROutputStream out) throws IOException {
        out.writeEncoded(INTEGER, bytes);
    }

    public int hashCode() {
        int value = 0;

        for (int i = 0; i != bytes.length; i++) {
            value ^= (bytes[i] & 0xff) << (i % 4);
        }

        return value;
    }

    boolean asn1Equals(DERObject o) {
        if (!(o instanceof DERInteger)) {
            return false;
        }

        DERInteger other = (DERInteger) o;

        return Arrays.areEqual(bytes, other.bytes);
    }

    public String toString() {
        return getValue().toString();
    }
}
